Sequencing and analysis of mumps virus vaccine strain S79 Genome

Abstract

Objective To analyze the genome sequencing of mumps virus strain 79 purified from working seeds plague and examine its phylogenetic relationship with wild type virus strain isolated in China,and to explore the efficacy of vaccine at molecular level.Methods Whole genome sequences of two substrains of S79(major and minor),were obtained with fragment amplification by RT-PCR.Genetic distances between S79 and strains identified in China were analyzed based on the phylogenic analysis of small hydrophobic protein(SH) sequences.Results The nucleotide homologies of two S79 substrains(major and minor),with a ratio of 2:5 during culture,with Jeryl Lynn(JL) strain were 99.7% and 100%,respectively.There were scattered non-homologous recombination between two substrains.The genetic distances between strain S79,which was genotype A,and wild type virus strain identified in China,which were genotype F,was 11.2% -20.0%.S79 live vaccine was composed of two substrains,major and minor component,which were highly similar to JL strain in their genome sequences,but different from JL in their ratios during culture.Conclusion Different from wild type virus strain identified in China,the genotype of S79 was A,and phylogenetically distant from other strains,which may account for the low efficacy of S79 live vaccine.The ratios of two substrains might also be of interest for further study of the vaccine protection and efficacy. Key words: Mumps virus; Plague purification; RT-PCR; Sequence analysis; S79